Our Collective Brain
Culture is humanity's nervous system. Our culture controls society in a manner analogous to how our nervous systems controls our bodies. Our brains are diffusely controlled networks of neurons, each neuron firing and resting according to the other neurons within its vicinity. Various outside stimuli--like sound, heat, or light--excite batches of neurons and this excitation is propagated through the rest of the network. My argument is that this spread of information is similar to what allows our society to function.
I think it's believable to say that the biggest leap in humanity's intellectual capacity was when humans learned to communicate with each other through abstract symbols. These symbols allowed humans to reason and discern their environment with a greater clarity than ever before. It also allowed them to plan about the future. Eventually it evolved into language, which was a very important step in our ability to communicate with each other. The majority of human communication is physical rather than verbal, which is a pretty good indication that spoken language evolved after body language. This was probably the most important stepping stone on humanity's ascent to global domination. Rather than small tribes of people acting individually, our communication systems allowed us to transmit information about the world as a whole. Rather than each human thinking up a separate survival strategy on his or her own, the mental burden of planning could be spread across the entire group. This sort of collective computing strategy is so fundamental to human biology that is built into our genetics. Humans are incessant talkers--if you put a human in solitary confinement he will probably start talking to himself out of desperation. We can't help it, and we can't help it for a very important reason. Our survival depends on efficient communication among the group. This is because the conditions when early tribes of humans were most likely to survive involved intense and incessant communication with each other. Humans did not conquer the rest of animal kingdom as a result of our individual superiority over other animals. Humans conquered the animal kingdom because we could communicate more efficiently than other animals. Humans behave intelligently because human intelligence extends beyond the realm of any one monkey. Humans are intelligent because we have culture.
Culture allows the symbols we create--language, music, and images, among other things--to spread quickly through a group of people of any size. Richard Dawkins astutely observed that these symbols--his word for them was "memes"--evolved in a way similar to biological organisms. There symbols also tend to influence the actions of individuals within a group. Highly contagious symbols--sex, death, religion, gossip--are more likely to be widely spread among the population. These symbols, I would like to note, serve the same effect as electrical signals between neurons. They connect minds and allow groups of individuals to think about problems together.
Some may objectt that they are not influenced by culture, but that fact is that the roots of culture are so deeply embedded in human nature that some trace of it is unavoidable. Even the smartest humans of all time, people like Einstein or Newton, stood on the shoulders of those before them. The existence of really smart people like Einstein or a Newton is not evidence that individual humans are really smart, rather it is evidence that humans are really good at supporting each other. Other humans, who collectively gave these great people food, a place to live, an educational institution to reside in--not to mention other individuals who influenced these people's thinking--are what allowed humans to excel in intelligence. There may be other intelligent animals on the planet, but the reason we don't see any elephant Shakespeares or dolphin Beethovens is that dolphins and elephants don't have the rich opportunity that our human societies offer us.
Cultural evolution has therefore done as much to influence our place in the world as biological evolution. The cultural part of humanity is an extension of the biological part. In this way our brains extend beyond our physical bodies. Because of this, I think that the more we learn to understand our brains, the more brain-like our societies will become.